Practical considerations for reconstituting dairy powders to high solids content in a stirred-tank

This work considers the following practical aspects of reconstituting dairy powders to high solids content in a stirred-tank: solubility constraints, powder properties vs agitation, viscosity and age-thickening constraints. T he powders investigated were skim-milk, whole-milk, agglomerated whole-milk and whey. At a given temperature, component solubilities, in particular la ctose, place an upper limit on how high a solids content can be obtained. T he powders tested displayed differences in measured values of wettability, sinkability and dispersibility, however their reconstitution ability to hig h solids content was similar. The limiting factors, on how high a solids co ntent that could be attained, were either solubility limit or loss of vorte x. For reconstituted skim-milk, the viscosity increases exponentially with solids contents and will limit vortex formation and powder sinkability. In addition, at higher solids content, significant age-thickening of reconstit uted skim-milk occurred, whereby the viscosity of a 50% solids solution inc reased 3.5 times in 1 h, thus making the solution more difficult to handle.